7.3.3  Participants and setting

Details of participants and setting are collected primarily for presentation in the table of ‘Characteristics of included studies’. Some Cochrane Review Groups have developed standards regarding which characteristics should be collected. Typically, aspects that should be collected are those that could (or are believed to) affect presence or magnitude of an intervention effect and those that could help users assess applicability. For example, if the review authors suspect important differences in intervention effect between different socio-economic groups (examples of this are rare), this information should be collected. If intervention effects are thought constant over such groups, and if such information would not be useful to help apply results, it should not be collected.

 

Participant characteristics that are often useful for assessing applicability include age and sex, and summary information about these should always be collected if they are not obvious from the context. These are likely to be presented in different formats (e.g. ages as means or medians, with SDs or ranges; sex as percentages or counts; and either of these for the whole study or for each intervention group separately). Review authors should seek consistent quantities where possible, and decide whether it is more relevant to summarize characteristics for the study as a whole or broken down, for example, by intervention group. Other characteristics that are sometimes important include ethnicity, socio-demographic details (e.g. education level) and the presence of co-morbid conditions.

 

If the settings of studies may influence intervention effects or applicability, then information on these should be collected. Typical settings of healthcare intervention studies include acute care hospitals, emergency facilities, general practice, extended care facilities such as nursing homes, offices, schools and communities. Sometimes studies are conducted in different geographical regions with important differences in cultural characteristics that could affect delivery of an intervention and its outcomes. Timing of the study may be associated with important technology differences or trends over time. If such information is important for the interpretation of the review, it should be collected.

 

Diagnostic criteria that were used to define the condition of interest can be a particularly important source of diversity across studies and should be collected. For example, in a review of drug therapy for congestive heart failure, it is important to know how the definition and severity of heart failure was determined in each study (e.g. systolic or diastolic dysfunction, severe systolic dysfunction with ejection fractions below 20%). Similarly, in a review of antihypertensive therapy, it is important to describe baseline levels of blood pressure of participants.